Tilting cathode for ignitron



March 14, 1950 s. M. CORK ETAL TI'LTING CATHODE FOR IGNITRON 2Sheets-Sheet 1 Filed March 26, 1349 INVENTORS Spencer M. Cork 8\ John L.Boyer. BY

ATTORNEY WITNESSES:

Patented Mar. 14, 1950 TILTING CATHODE FOR IGNITRON Spencer M.Cork,.Macon, 6a., and- John L. Boyer,

Pittsburgh, la.,

assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application March26, 1949', Serial No.83,674

10 Claims. 1

Our invention relates to a vapor-electric device and particularly to asubstantially shockproof electric valve to be utilized on movingvehicles such as ships, locomotives and the like.

Vapor-electric devices, such as the ignitron, have been developed to apoint where, in relatively stationary mountings, they are deliveringvery reliable service over long periods of time. However, when anattempt is made to utilize these devices on moving platforms, such asvehicles, the shock and vibration produced by the motion of the vehicleshas produced serious inconveniences and unreliability in the operationof the devices.

According to our invention, we have constructed a vapor-electric devicein which the inconveniences resulting from shock and vibration aresubstantially eliminated and in which the various component partsoperate with substantially the same reliability as has heretofore beenobtained in stationary devices. Not only does the shock tend to hurlportions of the liquid cathode material about the container with greatviolence but also the component parts such as the electrodes, thevarious seals and insulators are also shaken about and frequentlydamaged either by the mechanical stresses set up by the motion or byelectrical stresses presumably intensified because of the presence ofliquid cathode material at unexpected portions in the container orbecause of the mechanical movements of the various parts.

The various exciting electrodes utilized to establish and maintain acathode spot on the cathode material have heretofore been directlymounted on the lead-ins for such electrodes. However, in a movingdevice, the weight of the electrodes will either bend the lead-in stemsor crack the insulating bushings or otherwise seriously interfere withthe normal operation of the device. To counteract this, we have providedseparate insulating supports for the electrodes coupled with separatelead-in bushings of relatively low inertia.

Also, it has been found that in this type of service cathode spots occurat the junction of insulating and conducting materials and while theexact reason for such appearance is not known, we believe that theaccumulation of dirt andpossibly small particles of cathode material atthe junction of the insulating and metallic portions have tended to theaccumulation of electric charges which break down and establish acathode spot substantially in the same manner as the ignitors establisha cathode spot on the 2. liquid electrodes. However, regardless of themethod offormation' of these undesirable or parasitic cathode spots, wehave found that by shading the junction of the metal and insulatingmaterial, these unwanted cathode spots are substantially eliminated.

Considerable di'fliculty has also been encountered because of thesuspended mass of the major electrodes, such as the anode and the anodeshields. It has accordingly been found necessary to use a method ofsupporting the anode so that it is mechanically supported byreinforcements of the vacuum seals betweenthe container and the anodestem and to make these vacuum sealsv of a relatively thin materialhaving relatively" small mass. Also, we have provided a method ofmounting the anode shields so that they are substantially rigidregardless of the motion of the container.v

We have further found that by shaping the anode shields they can be madeto substantially withstand even heavy masses of cathode material which'might be hurled against them without damage or material transmission ofthe cathode liquid to. the an'odesurfaces. Also, we have found thatbymaking the active shield surfaces as a segment of a sphere, they notonly have great mechanical strength but present a maximum of opening forthe passage of the current-carrying arc itself.

Because of the relatively great movement of portions of the cathodematerial, there is a tendency to carry into the cathode a substantialamount of foreign material such as material eroded off the anodes, theshields or other portions of the devices so that in time the cathodebecomes polluted and the reliability is materially afiected.

Accordingly, we have provided a collecting shield so that the cathodematerial returns to thecathode between the edge of the cathode cup andthe shield which extends from, or abovethe upper edge of the cathode cupto a point substantially at the bottom of the cup whereby foreignmaterial is trapped between the dirt shield. and the edge of the cup,and the cup itself, together with the shield, is contoured so that asthe. cathode material is inclined in various directions, it will notoverrun the edge of the cup or of the dirt-collecting shield.

In order to prevent portions of the cathode material from being thrownout of the cup by violent motion transmitted to the container, we havefilled the cathode pool substantially to the normal working level with amass of metallic mesh material and anchored the same firmly to theinside of the cup. Preferably, the mesh material is provided withrelatively small openings so that the cathode material will freely flowtherethrough at a relatively low speed, but will be impeded when itmoves at high speed, so that there is little tendency for the cathodematerial to be thrown off because of violent motion imparted to thecontainer.

In order to prevent cathode material from random motion from the cathodein the direction of the anode, we have provided a cathode shielddirectly above the cathode cup and firmly anchored to the container sothat any mass of material striking the shield will be deflected towardsthe bottom portion of the container. To prevent loose cathode materialfrom ascending along the wall of the container, 2. bafiie plate havingannular shape is rigidly secured to the side of the container so thatany cathode material running along the side of the container will beintercepted and returned to the vicinity of the cathode.

It is accordingly an object of our invention to provide a substantiallyshockproof vapor-electric device.

It is a further object of our invention to provide an improved cathodeassembly for a vaporelectric device.

It is a further object of our invention to provide an improved mountingfor the electrodes of a vapor-electric device.

It is a further object of our invention to provide mountings which willrigidly hold the various elements in position,

It is a further object of our invention to pro vide insulating mountingswhich are protected against unwanted cathode spot formations.

Other objects and advantages of our invention will be apparent from thefollowing detailed de scription taken in conjunction with theaccompanying drawings, in which:

Figure l is a sectional elevation of a vaporelectric valve according toour invention;

Fig. 2 is a perspective view of a cathode assembly according to ourinvention;

Fig. 3 is a sectional elevation through an insulating support accordingto our invention;

Fig. 4 is a modification of the insulating support as shown in Fig. 3;and

Fig. 5 is a shielded lead-in connection according to our invention.

According to the exemplary embodiment of our invention, thevapor-electric device comprises an evacuated metallic container having asubstantially tubular body portion I closed by the bottom or cathodeheader 2 and a top or anode header 3. A cathode cup 4 of relativelysmall diameter is set into the cathode header 2 and an anode stem 5 isattached to and extends through the anode header 3 and supports an anodeB for cooperation with the cathode I.

The cathode assembly comprises the substantially flat header 2 securedinto the body portion i of the container usually by Welding and has inthe center thereof the cathode cup 4 of relatively small diametercompared to the diameter of the container and having the top edge 8contoured or established at different levels so that the container maybe inclined various amounts in various directions without spilling thecathode material 5 over the edge 8 of the cup 4. The lowermost point orpoints at the contoured rim 8 is made flush with the header 2 so thatany cathode material on the header will drain into the cup 4. At aposition intermediate the ends of the cup 4 and adjacent the normaloperating level of the cathode material 'I, an enlargement orreservoir-like device 9 is supplied to supply sufficient cathode vaporfor normal operation of the device without materially lowering thesurface of a cathode material I in the cup 4.

In order to prevent foreign material from contaminating the surface ofthe mercury l in the cup, a dirt guard or shield ID is provided in theform of a substantially tubular member rigidly supported inside thecathode cup 4 but spaced inwardly from the edge 8 thereof. The top edgeH of the dirt barrier H) corresponds in shape to the contoured edge ortop 8 of the cathode cup 4. The bottom portion IQ. of the cathode cup 4is re-entrant to provide a minimum of cathode material I with thenecessary ignitor immersion over various degrees of inclination oi thevalve or the cathode material I therein.

In order to prevent rapid movement of the cathode material I because ofviolent motion imparted to the container, a mass of mesh-like materiali3 is firmly anchored in the cathode cup 4 and fills the same to justbelow the normal work ing surface of the cathode material I. Meshmaterial I3 is relatively fine so that while the cathode material I suchas mercury, gallium. cesium, rubidium, indium, potassium or sodium, mayreadily flow at relatively slow speeds therethrough, it will besubstantially impeded when violent motion is imparted to the material,

In order to allow the starting electrodes to properly cooperate with thecathode material 1 to maintain excitation under the various operatingconditions, a plurality of make-alive electrodes M are utilized andextend into holes or openings 15 which may be drilled or otherwiseprovided in the mesh-like material l3. Regardless of the motion of thecathode material, at least one or more of the openings 15 in the mesh l3will almost certainly be provided with sufllcient cathode liquid toestablish contact with one or more of the make-alive electrodes l4 sothat cathode spot will be established with maximum certainty when animpulse is applied to the make alive electrodes [4. In order to maintainthe cathode spot until such an interval as the main anode 8 may pick up,we prefer to provide one or more keep-alive type electrodes IS in theimmediate proximity to the cathode surface.

In order to prevent displacement of the auxiliary electrodes l4 and IEor the breaking of the seals, we have provided a special mounting forthe electrodes 14 and 16. This mounting preferably takes the form of aninsulating body or bushing I! mounted on a pin or bolt 18 which isrigidly secured to the header v2 or other portion of the containerusually by means of welding. In order to prevent direct contact of theedge of the insulator I? with the metal of the header 2, a washer orbushing I9 is provided between the metal of the header 2 and theinsulating body I! so that the junction 29 between the metal and theinsulating material I l is shaded by a relatively deep crevice-likepassage 2| to prevent formation of a cathode spot because of theaccumulation of a. charge for any reason adjacent the edges of theinsulator H. The top end of the insulator IT is provided with a cap 22which err-- tends across the surface of the insulator I! and is likewiseprotected from contact with the insulator by means of an undercut orundersized washer or bushing 23. The whole is securely attached andrigidly connected, preferably by means of a screw connection between thebolt [8 and a nut 24 which is then pinned or otherwise rigidly securedin position after it is tightened in place. As the vibration sometimestends to rotate the bushing I! on the stem l8 an interlock is frequentlyapplied. A satisfactory interlock comprises a flat surface H! on theinsulator l1 and a washer I02 having a portion I04 deformed into contactwith the portion 1' In those locations where liquid mercury or othercathode material might tend to flow on the top of the insulator I1, itis sometimes desirable to provide a skirt-like portion 25 on the cap 22extending part way down over the surface of the insulator I! in spacedrelation thereto. It is also sometimes desirable to increase thecreepage distance across the surface of the insulator I! by providinggrooves I6 or ridges on the surface of the insulating material.

In operation a conducting layer is gradually formed on the surface ofthe insulator in the positions exposed to the action of the arc stream.The use of the shading grooves 2| and 26 or the skirts 25 materiallyretards the formation of these conducting layers and greatly prolongsthe useful life of the device.

The electrode support 21 is connected intermediate the ends of theinsulating body I! and rigidly connected thereto by pulling the samefirmly in contact with the material and securing in that position,preferably by welding. It is desirable in most cases to provide agroove-like receptable 28 for securing and rigidly holding the support21 in position. As shown in Fig. 3, this may be done by providing agroove around the exterior of a substantially unitary or solid bushingI! or, as shown in Fig. 4, this may be accomplished by providing abushing in a plurality of sections including an inner portion 44 and aplurality of outer portions 29 which clamp the electrode supports l and3| firmly between.

The lead-in connections for the auxiliary electrodes are made completelyindependent of the electrode supports and are constructed of as smallmass as possible and securely shielded to prevent improper contact bythe lead-in with the loose cathode material, and deterioration from heator coating of the insulator by conducting matter. We prefer to constructthese lead-ins as relatively small lead-in wires 32 extending ininsulative relation to a relatively light thimble or eyelet 33 andsealed thereto by means of a vitreous seal 34. The eyelet 33 is thenextended through a suitable opening 35 in the heater 2 or other portionof the container and secured thereto, preferably by projection welding.A sleevelike guard or shield 36 is placed around the eyelet 33 and itsinsulating portion 34, preferably substantially concentric therewith andsecured usually by welding to the inner surface of the header 2.

Usually, it is desired to provide an opening 31 at the bottom of theshield 36 so that any mercury or material which should be condensed orotherwise be formed inside this sleeve or shield 36 will readily draintherefrom. The shield is completed by a relative disk-like cap 38secured to the lead-in wire 32 or stem. Preferably, the disk 38 extendsover the end of the tubular shield 36 and in spaced relation thereto. Aconnection from the lead-in32 to its associated auxiliary electrode l4or MS is provided by means of a resilient connection of low mass,preferably in the form of a laminated or multiple layer of straplikematerial 39 which is secured by welding or other suitable means both tothe lead-in stem 32 and the support 2! of the electrode, preferablythis-strap-like connection 39 is of substantially S-shaped formation totake up any shock which might be transmitted to it.

Since in normal operation of the device, the cathode material 1 will beconstantly being condensed and returned to the cathode cup 4 over thecathode header 2, it is usual that condensed cathode material orfreecathode material Will be found on the header 2. In the event of shockbeing transmitted to the container, this material has a tendency to flowup alongside of the container and could possibly be projected intocontact with the electrodes at the top or anode end of the container. Toprevent this, we have provided an annular baffle 40 rigidly connected tothe external wall of the container and having a central opening 4| forthe passage of the arc.

Preferably, this annular baffle 40 is substantially cone-shaped with thelittle end extending in the direction of the cathode so that any cathodematerial coming in contact with the baflle 40 will be returned to thecathode end of the device. To further impede the flow of loose cathodematerial, a substantially disk-like baflle 42, preferably concave in thedirection of the cathode, is rigidly mounted above the cathode cup 4 andbetween the anode and cathode so that any material flowing from thevicinity of the cathode will be impeded in its motion toward the anode6.

The anode stem or anode lead-in is mechanically supported in aninsulating bushing 43 which is rigidly attached to the anode header 3and can be composed of any suitable material, although we have foundthat a solution of glass and mica with suitable metal supports providesa desirable rigid mounting support with great resistance to damage byimpact by motion of the device. Since these rigid mechanical supports 43offer poor vacuum seals, we have provided a vitreous metal seal 45 ofsmall mass in parallel with and substantially independent from thesupporting insulator 43. Preferably, this independent seal 45 iscomposed of a plurality of vitreous sleeves 4641 having sealing bushings484950--5l sealed into the vitreous sleeves 46 or 41 and welded tovarious portions of the anode stem 5 or header 3. The anode 6 itself issupported at the lower end of the anode stem 5 and the working facecomprises a spherical sector 52 to provide a maximum of working face fora given diameter. In insulations having severe shock the anode 6 may bemounted on the insulating supports and the anode lead-in may be onlystrong enough to properly carry its own weight. The anode shields 53--54and 55 are constructed as substantially concentric cylinders rigidlymounted in various portions of the container and having the workingfaces concentric and closely spaced to each other or to the anode sothat the working faces of the anode shields 53, 54, 55 are likewisespherical segments 56, 51 and 58 which are provided with a plurality ofpassages 59 for the major current carrying arc in the device. Thisspherical shape not only gives great mechanical strength from shock orfrom contact with flying portions of cathode material but also providesa maximum of passage opening for the diameter of the anode shield. Asthe concentric anode shields approach the anode 6 the spherical facesare of smaller area. In order to increase the effective are area weprovide lateral passages 62 in the inner shield 53 and lateral passages63 in the intermediate shield 54. The lateral passages 62 and 63 aresufiicient in number to produce approximately the same are concentrationin the passages at each shield. The shields 53 and 54 are usuallyconstructed of refractory metal to lpI'BVEIIt burning.

The innermost shield 53 conforms substantially to the shape of the anode6 and its anodestem 5 so that the shield 53 is effective throughoutsubstantially the full length of the anode 6 and its lead-in stem 5. Itis preferably anchored intermediate the insulating support 43 for theanode stem 5 and if desired may be supplied with control potential atits mounting point 60. The anode shields 54 and .55 are preferablymounted on the anode header 3 by means of rigid insulating supports suchas disclosed in Fig. 3 or .4 and hereinbefore described. If desired,lead-inconnections 8| similar to the lead-in connections for theauxiliary cathode electrodes l4 .or 16 may be supplied for the variousanode shields. We prefer to utilize insulator supports of the type shownin Fig. 3 for the cathode electrodes and to utilize the type shown inFig. 4- for the anode electrodes or shields, but obviously either typemay be used at either position.

While for purposes of illustration, we have shown an exemplaryembodiment of our invention and described our invention to the best ofour present ability, we desire it to be understood that further changesand modifications can be made therein without departing from the truespirit of our invention or the scope of the appended claims.

We claim as our invention:

1. In a vapor-electric device having a metal container, an electrodesupport comprising an insulating bushing, a metal fastening membersecuring said bushing to a portion of said container, an interlocktoprevent relative movement of said bushing with respect to saidcontainer, a metallic shield attached to the fastening member andcovering the end of the bushing remote from the portion of thecontainer, a skirt on said shield extending in spaced relation to aportion of the sides of said bushing and an electrode support securedintermediate the ends of said I securing said bushing to a portion ofsaid container, an interlock to prevent relative movement of saidbushing with respect to said container, a metallic shield attached tothe fastening member and covering the end of the bushing remote from theportion of the container, a skirt on said shield extending in spacedrelation to a portion of the sides of said bushing and an electrodesupport secured intermediate the ends of said bushing, a lead-inextending through a portion of the container, an insulating seal betweensaid lead-in and said container, a sleeve surrounding said lead-in inspaced relation thereto, said sleeve being secured to said container, adisk-like shield secured to the lead-in and extending in spaced relationto the end of the sleeve and a resilient conductor attached to saidlead-in and said electrode support.

3. In a shock resistant vapor-electric device, a cathode assemblycomprising a metal header, a

deep cathode cup secured to said header, the top 1 of said cup beingcontoured and having the lowermost portion of the edge flush with theheader, a dirt screen in said cup, said screen conforming in shape tothe contour of the cup and extending in spaced relation to the side ofthe cup to a point adjacent the bottom of the cup, a quantity of liquidcathode material in said cup, a mass of wire mesh firmly secured in saidcup and extend ing substantially to the normal operating surfaceposition of the cathode liquid, a shield firmly anchored above thecathode cup, a plurality of exciting electrodes cooperating with saidcathode, each of said exciting electrodes being firmly mounted on saidcathode header by means of an insulating bushing, a metal fasteningmember securing said bushing to a portion of said container, aninterlock to prevent relative movement of said bushing with respect tosaid container, a metallic shield attached to the fastening member andcovering the end of the bushing remote from the portion of thecontainer, a skirt on said shield extending in spaced relation to aportion of the sides of said bushing and an electrode support securedintermediate the ends of said bushing a lead-inextending through aportion of the container, an insulating seal between said lead-in andsaid container, a sleeve surrounding said lead-in in spaced relationthereto, said sleeve being secured to said container, a disk-like shieldsecured to the lead-in and extending in spaced relation to the end ofthe sleeve and a metallic strap conductor attached to said lead-in andsaid electrode support.

4. In an electric discharge device having a metallic header, aninsulating support on the inner side of said header, an electroderigidly mounted on said insulator, a lead-in independent of said supportand a resilient connection between said lead-in and said electrode.

5. In an electric discharge device having an evacuated container, ametal header, a cathode cup secured in said header, an insulatingbushing secured on the inner side of said header, a metal cap secured atthe top of said bushing, skirts on said cap extended in spaced relationto a portion of the sides of said bushing, an electrode support rigidlysecured to said bushing intermediate the ends thereof, an electrodeattached to said support, a lead-in extending in insulated relationthrough said header and a resilient connection between said lead-in andsaid electrode.

6. An entrance bushing for an electric discharge device having a metalcontainer, there being an opening in said container, a lead-in extendingthrough said opening, an insulating seal between said lead-in and saidcontainer, a substantially tubular shield surrounding said lead-in, saidtubular shield being secured to the container, a cap-like shield securedto the lead-in and extending in spaced relation to the end of thetubular shield.

'7. In an arc discharge device having a metal container, an electrodeassembly comprising an insulating body rigidly attached to the interiorof the container, an electrode support firmly attached intermediate theends of said bushing, spacer means providing a narrow shading space atthe junction of the insulating member and the container, an electrodemounted on said support, a lead-in extending through said containenaninsulating seal between said lead-in and said container, a shield aroundsaid seal and a resilient connection between said lead-in and saidelectrode support.

8. An insulating mounting for an electrode of a vapor-electric devicehaving a metal container comprising a bolt rigidly connected to thecontainer, an insulating body around said bolt, a spacer between saidinsulating body and said container, a cap on said insulating body, aspacer between said cap and said insulating body, fastening means forsecuring said parts in assembled relation and means for mounting anelectrode support intermediate the ends of said insulating body.

9. A shock resistant vapor-electric device comprising an evacuated metalcontainer, said container having a substantially tubular body with endheaders, a cathode assembly on the bottom header including a relativelynarrow cathode cup united to said header, a pool of cathode liquid insaid cup, means secured in said cup tending to prevent displacement ofsaid cathode material, a plurality of exciting electrodes extending intoproximity with the cathode, an insulating support for each of saidelectrodes, means for shading the point of contact between the containerand the insulating support, a lead-in for each of said excitingelectrodes, an insulating seal for each leadin, a shield surroundingeach of said seals, a re- 10 silient connection between each of thelead-ins and its associated electrode.

10. A vapor-electric device comprising an evacuated container, a cathodeheader at one end of the container, an anode header at the opposite endof the container, a cathode cup set into said cathode header, aplurality of exciting electrodes mounted on said cathode header, alead-in for each of said exciting electrodes independent of themounting, an anode, an insulating support for said anode, an insulatingvacuum seal independent of said mounting, a plurality of anode shieldssurrounding said anode, insulating mountings for said anode shields,said shields having substantially spherical arc passage faces.

SPENCER M. CORK. JOHN L. BOYER.

No references cited.

